vdso/datapage: Correct struct member kernel-doc

vdso/datapage: Correct struct member kernel-doc

Remove the "[]" array indicators from the struct member descriptions
to avoid kernel-doc warnings.

Warning: include/vdso/datapage.h:107 struct member 'basetime' not
 described in 'vdso_clock'
Warning: include/vdso/datapage.h:107 struct member 'offset' not described
 in 'vdso_clock'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260228071711.2663851-1-rdunlap@infradead.org